Overload electric switch



y 3, 1956 NOBORU MAEDA OVERLOAD ELECTRIC SWITCH Filed May 16, 1955 INVENTOR M )fi W,

ZZ%F e Y ATTORNEYS United rates Patent OVERLOAD ELECTRIC SWITCH Noboru Maeda, Saijo-cho, Hiba-gun, Japan Application May 16, 1955, Serial No. %,714 In Japan October 20, 1949 Public Law 619, August 23, 1954 Patent expires October 20, 1969 3 Claims. (Cl. 200-416) This invention relates to an overload electric switch and more particularly an electric switch having a thermally responsive latch for releasing a spring contact biased toward open position in the event of an overload.

Objects of the invention are to provide overload electric switches which comprise but few and rugged parts and which are reliable for both manual operation and for automatic opening in the event of an overload. More specifically, an object is to provide an overload electric switch in which the normally stationary contact member is spring biased to separate from the movable contact and is retained in circuit-closing position by a bimetallic latch forming a series circuit element of the switch.

These and other objects and the advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Fig. 1 is a plan view of an overload electric switch embodying the invention;

Fig. 2 is a side elevation, with parts broken away and others in section, of the switch in normal switch open condition;

Fig. 3 is a side elevation of the same as seen immediately after automatically opening under overload;

Fig. 4 is a side elevation of the switch as reset, but still open, after an automatic opening; and

Fig. 5 is a perspective view of the bimetallic latch and normally stationary switch contact.

in the drawing, the reference numeral 1 identifies a base of insulating material on which the conductive portions of the switch are mounted and which will be housed in the usual metal switch box which, for clarity of illustration, is not shown. The base has secured thereto or integral therewith a rectangular block 2 of insulating material in which is embedded a stud 3 which constitutes one terminal of the switch. The normally stationary contact of the switch comprises an inverted metal channel strip welded or brazed to a leaf spring 5 which fits over th terminal stud 3 and is clamped flush with the top of block 2 by a nut 6.

For convenience of description, the right end of the switch will be considered to be the rear end and block 2 will be termed the rear block to distinguish from a front block 2/ of insulating material which may be integral with or secured to base 1.

The base of metal U-shaped bracket 7 is secured to the base 1 between blocks 2 and 2', and each arm of the bracket is provided with a forwardly opening slot 8 having: semi-cir ular upper and lower ends constituting bearings for the shaft 2) of an insulating material switch lever 10 and for an arcuate boss 11 stamped laterally from a side 12 of a saddle-shaped movable contact having a base 13. The customary toggle arrangement for rocking the movable contact is formed by an arm 14 depending from lever 19 and a helical spring having its end anchored in an opening in base 13 of the movable contact. The opposite end of spring 15 is connected to the lower end of arm 14. The forward ends 12 of the sides 12 of the moving con- 2,753,417 Patented. July 3, 1956 ice tact are slightly flared to fit about the flanges of the stationary contact 4 when the switch is closed.

In accordance with the invention, the web of the contact 4 is cut away to provide an opening 16 which extends from in front of the forward edge of switch lever 10 to somewhat in front of that part of the contact engaged by the rear end of switch iever 10, and the front end of contact 4 is normally seated beneath an insulating material latch 17 mounted on a bimetallic bracket 18 which is secured to the base 1 by a terminal stud 19 and electrically connected to the bracket 7, and thereby to the movable switch contact. Current therefore flows through the bimetallic bracket 18 when the switch is closed and, in the event of an overload, the bracket flexes to withdraw the latch 27 from the end of contact 4 and the latter is separated from the moving contact by the leaf spring 5, see Fig. 3.

Upon cooling of the bracket the switch may be reset by turning the lever clockwise to restore the moving contact to open-switch position, see Fig. 4. The rear end of lever 10 engages the contact 4 back of the opening 16 to force the same back to normal position in engagement with the tops of the insulating blocks 2 and 2'.

So long as there is no overload, the switch is operated manually as a conventional toggle switch but, in the event of an overload, it opens automatically and may be reset simply by manually opening the switch.

While a single pole switch with toggle operating mechanism has been illustrated and described, it is apparent that the invention may be incorporated in multipole switches and that other than toggle mechanisms may be employed for manual operation of the movable contact.

I claim:

1. A manually operable overload electric switch comprising a normally stationary contact of metal strip form, a base of insulating material including spaced front and rear blocks of insulating material on which said contact strip is normally seated, means securing the rear end of said contact strip to the rear block and biasing the forward portion of the contact strip to separate from the front block, a movable contact, means supporting said movable contact, manually operable means to move said movable contact into and out of engagement with said contact strip when its forward portion is seated on said front lJlOC.(, a bimetallic strip connected in series with switch con [acts and carrying an insulating material latch engageable with the front end of said contact strip to retain the forward portion of said contact strip seated on said front block.

2. A manually operable overload electric switch as recited in claim 1, wherein said movable contact is located between said blocks of insulating material and said manually operable means inciudes a lever of insulating material pivotally supported above the movable contact and having a rear end to engage said contact strip to force the same into normal position with its forward portion seated on said front block, said contact strip being provided with an opening to clear the forward end of said lever.

3. A manually operable overload electric switch as recited in claim 2, wherein said supporting means comprises a U-shaped bracket secured to said base between said blocks, each arm of said U-shaped bracket having a forwardly opening slot whose upper and lower ends provide bearings for said lever and said movable contact respectively.

References Cited in the file of this patent UNITED STATES PATENTS 2,053,629 Petersen Sept. 8, 1936 2,148,880 Sattler Feb. 28, 1939 2,150,013 Von Hoorn Mar. 7, 1939 

